The food processing industry, including the poultry, beef, pork, seafood and vegetable processing segments, is a heavy user of water. In poultry processing, for example, governmental regulations concerning the operation of processing plants require water cooling as a final step before packaging the birds. As a part of this procedure alone, an average size plant may use 50,000 or more gallons of water per day. Large quantities of water are also employed in other aspects of poultry processing. For example, high temperature water is used for washing and scalding the birds prior to defeathering. Water is also used for evisceration and for general clean-up of the plant facilities. Proper and effective treatment of the resulting effluent water from these and other food processing applications is a concern of great economical and environmental significance.
The search for an ecologically sound and cost efficient method for treating such waste water, with its generally high and varied organic solids content, has, however, been a disappointing one. Although a number of different methods have been tried, many of these processes have had significant drawbacks associated with their use.
One method frequently employed by the food processing industry in treating their waste effluent involves the use of metal salts, such as ferric chloride, ferric sulfate and aluminum salts (alum), to initiate the coagulation of suspended solids for eventual removal. However, although the solids found in food processing waste streams, with their high protein, lipid and carbohydrate content, have potential as an inexpensive and highly nutritive feedstock additive, the use of such metals in the treatment process severely limits these applications. Ferric compounds, for example, cause rapid biological deterioration of the solids, including rapid elevation of free fatty acid levels. The metals also cause unsatisfactorily high initial peroxide levels and discoloration of the solids. Moreover, the presence of these metals in processed feedstocks can result in significant health problems in consuming animals, including such afflictions as chick edema or rickets, if ingested in large quantities. Indeed, feedstocks containing solids from metal treated waste water are generally of poor grade, off color, low palatability and poor digestibility. These metals also contribute to a strongly offensive odor in the clarified effluent, and microbial action also remains a problem. Furthermore, environmental concerns abound when land disposal, an alternative to feedstock applications, is considered for metal treated waste solid. If careful landfill precautions are not taken, the metals can leach out and contaminate water supplies. As a result of these and other concerns, governmental disposal requirements of metal treated wastes are becoming more restrictive, and in some instances certain land disposal options have been totally prohibited.
Another commonly used waste treatment process includes the use of synthetic polymers, such as polyacrylamides, as flocculants and/or coagulants for solids removal. However, the presence of synthetic polymers in the resulting solids mass also causes problems in recycling the solids as feedstock additives. The polymers, for example, tend to bind tightly with water, requiring large energy expenditures just to remove sufficient water to meet food grade specifications. Moreover, the glue-like nature of the polymers causes a rapid accumulation of solids in the cooking apparatus during feedstock processing, resulting in serious equipment damage. For these and other reasons, feedstock producers often decline to accept such polymer-based materials. The polymers, with their high water content and low biodegradability, also present environmental concerns, necessitating at times restrictive and even prohibitive governmental policies on the disposal of such solids in landfills.
New and/or better waste treatment processes are needed. The present invention is directed to this end.